The present invention relates in general to shield apparatus for use in driving tunnels or similar excavations.
One well known form of shield or tunnelling apparatus has a series of cutting members or planks arranged side-by-side and supported by one or more frames. The cutting members are then advanced individually or in groups with the aid of hydraulic rams to effect the driving progress. In German Patent Specification No. 2021734 apparatus of this type is described wherein two frames are shifted alternately and support the aforementioned cutting members. The frames of this apparatus can be expanded, and to provide a rigid abutment for the shifting rams, the frames can be fixed to the floor of the working by means of anchoring pins driven into the floor by hydraulic presses. The frames can only be shifted when the anchoring pins are released. In this known apparatus additional components such as hydraulic props, horizontal bracing beams and transverse floor beams obstruct the open space inside the shield and it is difficult to use additional machinery inside the shield.
It is generally desirable to utilize cutting machinery which rests on the floor of the tunnel inside a shield since inter alia vibration caused by the operation of the machinery need not then be transmitted to the shield itself.
This necessitates a shield structure which is kept open at the floor but in this case the shield is not particularly stable and cannot resist side pressure so well as a shield braced at the floor.
A general object of this invention is to provide an improved shield apparatus wherein the floor region is basically unobstructed while there is adequate bracing against lateral forces.